Various processes for producing powders have been known and implemented at the industrial manufacturing scale for many years. Large scale production of powders can be classified in two general categories which include solid state methods and solution-based methods. Solid state methods are generally simple to implement but are typically time and energy intensive and often lead to relatively larger particle sizes and lower purity. They are almost always implemented as batch processes that lead to batch to batch variability. Solution-based methods generally tend to be more complex but often lead to relatively smaller particle sizes, more homogeneous and uniform particles, and with higher purity. Solution-based process can typically be operated continuously. However, solution based processes suffer from relatively low production rates compared to solid-state methods and are therefore used for only low volume specialty powders.
Large scale production of cathode materials for rechargeable batteries has gained significant attention in recent years due to the increasing popularity of such batteries for portable electronics and for electric and hybrid-electric vehicles. Both solid state and solution-based methods have been used to produce cathode materials for rechargeable batteries. See Toprakci et al., “Fabrication and Electrochemical Characteristics of LiFePO4 Powders for Lithium-Ion Batteries”, KONA Powder and Particle Journal, 2010:28:50-73; Jugovic et al., “A Review of recent developments in the synthesis procedures of lithium iron phosphate powders”, Journal of Power Sources 2009:190:538-544.
Solution based methods for producing cathode materials offer advantages of relatively smaller particle sizes, homogeneity and purity and typically require few processing steps but suffer from low production rates. Attempts at mass production of lithium based cathode materials using aerosols and gas burners have been disclosed. See, e.g., Ogihara et al., “Preparation and electrochemical properties of cathode materials for lithium ion battery by aerosol process”, Material Science and Engineering B 2009:161:109-114 and Myojin and Ogihara et al., “synthesis of non-stoichiometric lithium manganite fine powders by internal combustion-type spray pyrolysis using gas burner”, Advance Powder Technology, 2004:15:397-403. However, the production rates are still relatively low. Accordingly, a continuing need exists for improved production methods for producing powder for large scale manufacturing.